Strapping machine feed control

ABSTRACT

This machine straps a package with heat sealable plastic strapping. The strap is fed by motor driven geared feed and tension wheels around a yoke and against a stop. A loop of strap is developed which is sensed by a flag causing reversal of the motor, withdrawal of the loop and stopping of the motor. The operator then operates a valve to cause further reversal of the motor which tensions the strap around the package. An idler senses removal of slack in the drive chain from the motor when the strap is tight and this causes the motor to stop. The strap is gripped against a side-retractable anvil on opposite sides of a vertically moving platen and knive assembly, while straddling a retractable tongue. A heated blade replaces the tongue whereupon the platen squeezes the heated joint and cuts the strap. The anvil and tongue are withdrawn for removal of the strapped package. The platen, tongue, anvil and sealing blade are controlled by a set of cams on a linear actuator.

United States Patent [191 Goodley [111 3,841,213 1 Oct. 15, 1974STRA'PPING MACHINE FEED CONTROL [75] Inventor: George F. Goodley, Media,Pa.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: Feb. 14, 1973 [21] Appl. No.: 332,449

Related US. Application Data [62] Division of Scr. No. 198,862, Nov. 15,1971, Pat. No.

FOREIGN PATENTS OR APPLICATIONS Great Britain 100/26 PrimaryExaminerBilly J. Wilhite Attorney. Agent, or FirmC. E. Tripp [57]ABSTRACT This machine straps a package with heat sealable plasticstrapping. The strap is fed by motor driven geared feed and tensionwheels around a yoke and against a stop. A loop of strap is developedwhich is sensed by a flag causing reversal of the motor, withdrawal ofthe loop and stopping of the motor. The operator then operates a valveto cause further reversal of the motor which tensions the strap aroundthe package. An idler senses removal of slack in the drive chain fromthe motor when the strap is tight and this causes the motor to stop. Thestrap is gripped against a sideretractable anvil on opposite sides of avertically moving platen and knive assembly, while straddling aretractable tongue. A heated blade replaces the tongue whereupon theplaten squeezes the heated joint and cuts the strap. The anvil andtongue are withdrawn for removal of the strapped package. The platen,tongue, anvil and sealing blade are controlled by a set of cams on alinear actuator.

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LINEAR CAM LIMIT VALVE PE-Z I 60 I I HEAT SEAL FOOT VALVE FV OPENEDVALVE STRAP LIMIT I: U' EJ I MI As I T\ FLAG IO ON- v ALvE Aifis//TENSION WHEEL PE-I cld SOL S -L- I TENSION LIMIT VALVE TV STRAPPINGMACHINE FEED CONTROL REFERENCE TO RELATED APPLICATION This applicationis a division of Goodley, Ser. No. 198,862, filed Nov. 15, 1971 andassigned to the FMC Corporation and now Pat. No. 3,759,169 which issuedSept. 19, 1973.

Application Ser. No. 332,465, filed Feb. 14, 1973 is also a division ofthe aforesaid Goodley parent application and has claims directed tocontrol of the strap feed mechanism.

1. Field of the Invention This invention relates to apparatus forstrapping articles such as packages and more particularly to an improvedstrap feeder in a machine for strapping the packages with heat sealableplastic tape.

2. Description of Prior Art The apparatus of the present invention is animprovement over the U.S. patent to Billett et al. No. 3,269,300, Aug.30, 1966. The improvements are so numerous and varied that they can onlybe made clear after an understanding based on the apparatus of thepresent invention.

The US. patent to Plattner, No. 3,590,729, July 6, 1971, shows a smalldiameter feed wheel geared to a large diameter tensioning wheel in astrapping machine with the strap wrapped less than 180 around thetensioning wheel and not wrapping around the feed wheel at all.

The US. Fat. to Rogers, No. 2,880,666, Apr. 7, 1959 shows a tyingmachine for cord wherein the cord passes between geared togethertensioning wheels without wrapping around either wheel.

BRIEF DESCRIPTION OF THE MACHINE The mechanical features of thestrapping machine of the present invention will be briefly summarized.

The strap transport of the present invention comprises a feed wheel anda tension geared together. The feed wheel feeds the strap beneath afront gripper, between a side retractable tongue and a platen, between arear gripper and a side retractable anvil, up around a yoke, backbetween the front gripper and the anvil, over the tongue and against astop on the anvil. In accordance with the present invention, a slightoverfeed after the free end of the strap strikes the stop develops aloop, which closes the front gripper, reverses the feed motor toremovethe overfeed loop and stops the feed motor. I

The operator now operates a control valve which resumes reversal of thefeed to tension the strap around a package within the yoke. As claimedin the parent application, after the strap has been tensioned, a reargripper closes automatically to maintain the tension, and a linear camactuator starts advancing. As a result of actuator advance andretraction, the tongue is retracted, a heated sealing blade replaces thetongue between the end of the bight of the strap, a platen presses thejoint, the blade is withdrawn, the platen is raised further to squeezethe heated joint, the strap is cut off at the joint, the anvil andtongue are retracted together, the platen is lowered and the strappedpackage can now be removed. The anvil and tongue are automaticallyreturned to their initial positions andupon full retraction of theactuator the feed is automatically restarted and stopped in the mannerdescribed above.

SUMMARY OF THE INVENTION The strap transport comprises a transport wheelassembly comprising a feed wheel and a tensioning wheel geared together.The feed wheel feeds the strap beneath a front gripper, between a sideretractable tongue and a platen, between a rear gripper and a sideretractable anvil, up around a yoke, back between the front gripper andthe anvil, over the tongue and against a stop on the anvil. A slightoverfeed after the free end of the strap strikes the stop develops aloop, and a sensor at the tensioning wheel detects the loop formation. Acontrol responsive to the sensor closes the front gripper, reverses thefeed motor and hence the transport wheel assembly to remove the overfeedloop and stops the feed motor when the sensor responds to removal of theloop. The loop sensor comprises a movable flag overlying the wrappedportion of the tensioning wheel and the control reverses the motor uponpartial displacement of the flag by the loop and stops the motor aftermotion of the flag toward its initial position.

The operator now operates a control valve which resumes reversal of thefeed to tension the strap around a package within the yoke. An idler onthe drive chain for the tensioning wheel senses removal of the slack inthe chain when the strap has been pulled tightly around the package andthe control then stops reversal of the motor and hence furthertensioning of the strap. As

mentioned, after the strap has been tensioned, a rear gripper closesautomatically to maintain the tension, the linear cam actuator startsadvancing, and the ends of the tensioned strap are joined.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of thestrapping machine embodying the invention.

FIG. 2 is a horizontal section of the machine taken on line 2 2 of FIG.1 with parts broken away.

FIG. 2A is a schematic diagram showing the threading of strap throughthe machine.

FIG. 3 is a persp'ective of the feed and tensioning mechanism of thepresent invention.

FIG. 4 is a side view of the front of a machine with parts broken away.

FIG. 4A is a horizontal section of the strap tension valve operatortaken along line 4A 4A of FIG. 4.

FIG. 5 is an enlarged section taken on line 5 of FIG. 2.

FIG. 6 is an enlarged section taken on line 6 6 of FIG. 2.

FIG. 7 is a view from the rear of the machine taken on line 7 7 of FIG.2.

FIGS. 8 and 9 are perspectives showing the tongue and anvil operation.

FIG. 10 is a diagram showing threading of the strap through certainparts of the machine, as well as yoke details.

FIGS. ll, 12 and 13 are sections through the yoke taken as indicated onFIG. 10.

FIG. 14 is an exploded perspective showing feeding of the strap throughthe feed wheel casing structure.

FIG. 14A is a section through the casing structure of FIG. 14, taken asindicated on FIG. 7.

FIGS. 15 to 20 are operational schematic diagrams illustrating thesalient mechanical features of the invention at various portions of acycle.

FIGS. 21 to 26 are control diagrams showing how the operations of FIGS.are carried out in sequence.

DETAILED DESCRIPTION Mechanical Features Referring to FIG. 1, thestrapping machine of the present invention includes a main body orhousing 12 supported on legs 13 and mounting a flat upper table 14. Thetable is slotted at 16 to accommodate tensioning of a strap around apackage (not shown) on the table. A retractable anvil 18 (see also FIG.6) is at the center of the table 14. The strap S is fed from a tape reelin a manner to be described in detail presently around a yoke 20 thatsurrounds the package. After the feed, the strap is tensioned againstthe package, a heat sealed joint is made, the strap is cut and thestrapped package removed.

The break away plan view of FIG. 2 shows additional mechanical featuresThe anvil 18 is broken away in this view as is a retractable tongue 24(best seen in FIG. 6) to expose a vertically reciprocating platen 26that mounts a strap cutting knife 27 (see FIG. 5).

FIG. 2 also shows a heat sealing blade assembly indicated generally at28 and illustrated in its retracted position. A side view of the bladeappears in FIG. 6. Also appearing in FIG. 2 are a front gripper 30 and arear gripper 32 for holding the ends and the bight of the straprespectively. These grippers are operated by bell cranks; as seen inFIG. 5.

A strap transport mechanism in the form of a pair of geared togetherfeed and tension'wheels appears in FIG. 3. The strap enters from belowand is wrapped partially around a feed wheel 34, pinched between thatwheel and a tension wheel 36, wrapped around the tension wheel and fedon through the mechanism.

FIG. 2A (a simplified diagram) shows the path of a strap through theapparatus. The strap enters the feed wheel 34 from the tape reel(FIG. 1) passes between the feed and the tension wheels 34, 36, wrapsaround the tension wheel 36, passes beneath the front gripper 30, passesbeneath the tongue 24 and above the platen 26, passes between the reargripper 32 and the anvil 18, is threaded through the yoke 20, traversesthe entire yoke 20, passes between the front gripper 30 and the anvil18, passes between the tongue 24 and the anvil l8, and abuts a stop 19formed on the anvil.

Strap Transport Drive Referring principally to FIGS. 2, 3, 4 and 7, thetransport drive of the present invention includes a reversible air motorM has a sprocket 40, driving a chain 42, and a sprocket 44 on the shaft46 for the tension wheel 36. The other end of the shaft 46 mounts a gear48 which is meshed with a gear 50 of the same pitch diameter on theshaft 52 for the feed wheel 34. The feed and tension wheels 34,36 arecovered with friction bands 34a and 36a formed of 90 Durometerpolyurethane elastomer. In accordance with the invention of theaforesaid divisional application, Ser. No. 332,465, filed Feb. 14, 1973,the strap S is gripped between the wheels 34,36, but it wraps around thefeed wheel 34 for something over 90 and around the tension wheel 36 forsomething over 180. The wrap around the feed wheel 34 is adequate tofeed the strap through the path shown in FIG. 2A and the wrap around thetension wheel 36 is adequate to tightly tension the strap around thepackage before sealing the joint in the strap.

In accordance with the invention of this divisional application, inorder to operate a tension limit valve TV, for stopping the tensioningof the strap around the package, and to initiate other functions to bedescribed presently, an idler sprocket 60 (FIGS. 3,4 and 4A) is mountedon an arm 62 pivoted to the frame at 63 and connected to a link 64. Acompression spring 66 that is compressed between a nut on the link 64and a frame element 67 (FIGS. 4- and 4A) is used for taking up the slackin the chain 42. The idler link 64 also mounts a tab 65 (FIGS. 4 and 4A)which is held against the operating button of the tension limit airvalve TV, the construction being that the valve TV is closed when thereis a slack in the reach 42a of the chain 42 engaged by the idlersprocket 60. This slack occurs when the motor M is driving the wheels inthe feed direction illustrated by the solid arrow on the wheel 34 inFIG. 3. The slack tends to be removed from the idler side 42a of thechain 42 when the motor M is reversed to drive the tension wheel 36 inthe tension direction indicated on that wheel by the dashed arrow inFIG. 3. When the strap is tight around the package, the side 42a of thechain becomes taught, swinging out the idler arm 62, and pulling the tab65 away from the tension limit valve TV. This opens the air valve forstopping the motor M and for other purposes to be described presently.Opening of the valve TV only takes place upon the generation of apredetermined amount of torque required to drive the tensioning wheel36, which torque is sufficient to adequately tension the strap aroundthe article. Hence the action just described does not stop the motor Mfrom drive in the tensioning direction until the package is tightlystrapped.

Overrun Flag As seen in FIG. 7, and in accordance with the presentinvention, an overrun flag 70 is provided at the tension wheel 36 forsensing a loop in the strap that develops during the feeding operationand causing the loop to be removed before the strap is tensioned aboutan article.

The flag 70 is pivoted at 70a to a plate (shown in perspective in FIG.14) and has a loop sensing surface 70b that is contoured to fit thetension wheel 36. The flag 70 has a cam surface 70c for operating a camfollower 71. The follower 71 is pivoted to the plate 75 at 71a and has afollower roller 71b for depression by the 9 m SIH7ER1QJQZQ Ih l w 71 hasa cam surface 710 for depressing the operating arm 72 of a strap limitvalve SV, which occurs when the flag 70 is displaced by development of aloop as will be explained in detail presently.

FIG. 14 shows additional details of the housing and guide mechanismsassociated with the transport wheels. The strap enters between the guiderollers 69 (see also FIGS. 4 and 7), passes between vertical guides72,73 and wraps something over around the feed wheel 34, the positiononly of which is illustrated in FIG. 14. The strap S then passes betweenthe nip of the wheels 34 and 36 wrapping more than around the tensionwheel 36 (also not shown) passing a pocket 74 for the flag 70, justdescribed. The strap leaves the tension wheel 36 and passes over the topof the upper surface 76 of a plate 77, passes beneath the front gripper30, passes beneath the tongue 24 and above the platen 26, passes betweenthe rear gripper 32 and the anvil 18 and on through the yoke 20 (notshown). After emerging from the yoke, the strap rides over the uppersur-

1. Article strapping apparatus of the type wherein reversibLe, powerdriven strap transport wheel means feeds the strap through an articlereceiving yoke and against a stop, the end of the strap is gripped, thetransport wheel means is reversed to tension the strap; means foraccommodating development of a loop of strap at said transport wheelmeans after the end of the strap has been stopped, means for sensing thedevlopment of said loop, and control means responsive to said sensingmeans for reversing said transport wheel means from the strap feedingdirection to the strap tensioning direction, the improvement whereinsaid control means includes means for stopping rotation of saidtransport wheel means when said sensing means responds to removal ofsaid loop, and means for independently re-starting motion of saidtransport wheel means in the strap tensioning direction for completionof the tensioning operation.
 2. The apparatus of claim 1, wherein saidstrap transport wheel means comprises a feed wheel followed by atensioning wheel with the strap partially wrapped around the latter fordirecting the strap to said stop, said loop sensing means comprising amovable flag overlying the strap adjacent said tensioning wheel; theimprovement wherein said flag is curved to conform to the majority ofthe wrapped portion of said tensioning wheel, said control meansreversing the wheel means drive upon partial displacement of said flagby the loop, said control means stopping reversal of said transportwheel means after motion of the flag back towards its initial position.3. The apparatus of claim 2, wherein said control means does not stopthe drive reversal until the flag reaches its initial, pre-loop formingposition.
 4. The apparatus of claim 2, wherein said control meansincludes a circuit for conditioning the reverse drive for resumptionthereof under manual control for subsequent tightening of the strapabout an article within said yoke.
 5. The apparatus of claim 1,comprising means for sensing the tension of the strap as it is tightenedaround the article, and means for stopping the drive to said transportwheel means upon development of a predetermined strap tension. 6.Article strapping apparatus of the type wherein reversible, power drivenstrap transport wheel means feeds the strap through an article receivingyoke, the end of the strap is gripped, and the transport wheel means isreversed to tension the strap against an article, the bight of the strapis gripped, and the bight and end of the strap are heat sealed, meansfor sensing the torque required to turn the transport wheel means duringfinal tensioning of the strap, and control means responsive to saidtorque sensing means for stopping the tensioning drive to the transportwheel means; the improvement wherein said transport wheel meanscomprises feed and tensioning wheels geared together, a reversiblemotor, a drive wheel for the motor, a driven wheel for said tensioningwheel, an endless tension member connecting said drive and drivenwheels, said torque sensing means comprising idler means responsive toremoval of the slack in said endless member when said feed andtensioning wheels are driven in their strap tensioning direction, andmeans for connecting said idler means to said control means.
 7. Theapparatus of claim 6, wherein said reversible motor is an air motor,said control means including directional valve means for determining thedirection of rotation of said motor, said means for connecting saididler means to said control means comprising a tension limit valveconnected to said directional valve means.